Reserved Sandbox 329

INTRODUCTION
Terminal uridylyl transferases (TUTases) belong to a superfamily of polymerase ß nucleotidyl transferases. TUTases have been isolated from Trypanosoma brucei and also Leishmania ssp, parasites causing diseases in humans such as African Sleeping Sickness. TUTases function in RNA editing; more specifically they catalyze the reaction that adds UMP to a RNA substrate. Trypanosomal TUTases have RNA substrates that are shown to select for cognate nucleosides and provide a metal ion binding site for Mg2+ ions.

STRUCTURE
The uridylyl transferase bound ligand is an ATP complex with two Mg2+ ions, however many TUTases involved in RNA editing are shown to exhibit preference for binding to UTP instead. Three aspartate residues are conserved in TUTases, and are required for coordinating the Mg2+ ions in some TUTases. Thus, these aspartate residues are vital in catalyzing this reaction.